<!--
 * @Author: Rachel 943701297@qq.com
 * @Date: 2022-08-03 14:17:59
 * @LastEditors: Rachel 943701297@qq.com
 * @LastEditTime: 2022-08-04 15:09:30
 * @FilePath: \代码c:\Users\94370\Desktop\面向工作学习\笔记\learning-notes\Vue_Code\vue_2.x_doc_learning\3-侦听器watch.html
 * @Description: 侦听器实践尝试
 * 
 * Copyright (c) 2022 by Rachel 943701297@qq.com, All Rights Reserved. 
-->
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Vue2.x文档学习——侦听器watch</title>
    <script src="../js/vue.js"></script>
    <!-- 因为 AJAX 库和通用工具的生态已经相当丰富，Vue 核心代码没有重复 -->
    <!-- 提供这些功能以保持精简。这也可以让你自由选择自己更熟悉的工具。 -->
    <script src="https://cdn.jsdelivr.net/npm/axios@0.12.0/dist/axios.min.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/lodash@4.13.1/lodash.min.js"></script>
  </head>
  <body>
    <div id="watch-example">
      <p>
        Ask a yes/no question:
        <input v-model="question" />
      </p>
      <p>{{ answer }}</p>
      <div style="width: 400px; height: 300px">
        <img
          v-bind:src="url"
          style="background-color: pink; width: 100%; height: 100%"
        />
      </div>
    </div>

    <script>
      var watchExampleVM = new Vue({
        el: "#watch-example",
        data: {
          question: "",
          answer: "I cannot give you an answer until you ask a question!",
          url: "",
        },
        watch: {
          // 如果 `question` 发生改变，这个函数就会运行
          question: function (newQuestion, oldQuestion) {
            this.answer = "Waiting for you to stop typing...";
            this.debouncedGetAnswer();
          },
        },
        created: function () {
          // `_.debounce` 是一个通过 Lodash 限制操作频率的函数。
          // 在这个例子中，我们希望限制访问 yesno.wtf/api 的频率
          // AJAX 请求直到用户输入完毕才会发出。想要了解更多关于
          // `_.debounce` 函数 (及其近亲 `_.throttle`) 的知识，
          // 请参考：https://lodash.com/docs#debounce
          this.debouncedGetAnswer = _.debounce(this.getAnswer, 500);
        },
        methods: {
          getAnswer: function () {
            if (this.question.indexOf("?") === -1) {
              this.answer = "Questions usually contain a question mark. ;-)";
              return;
            }
            this.answer = "Thinking...";
            var vm = this;
            axios
              .get("https://yesno.wtf/api")
              .then(function (response) {
                vm.answer = _.capitalize(response.data.answer);
                vm.url = _.capitalize(response.data.image);
              })
              .catch(function (error) {
                vm.answer = "Error! Could not reach the API. " + error;
              });
          },
        },
      });
    </script>
  </body>
</html>
